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Question: If you have a ROSC and the patient re-arrests and is now in a shockable rhythm do you shock at the next highest setting or do you revert back to 200 joules?For example, if one shock delivered on scene for an adult at 200J, then ROSC, then rearrest – next shock (as I suggest) would be 300J.

In this case, 200J was enough electricity to convert the patient’s rhythm and achieve ROSC. In the re-arrest scenario, there is no current evidence suggesting the myocardium requires a higher dose of J then that given during the initial arrest. In fact, this would be a witnessed VF/VT and far more likely to respond to a lower dose of J, then a patient who has been in a more prolonged VF/VT. The evidence behind escalating doses is for subsequent shocks in non-terminating VF/VT.

Some evidence from the 2015 AHA guidelines:

There is no evidence indicating superiority of one biphasic waveform or energy level for the termination of ventricular fibrillation (VF) with the first shock (termination is defined as absence of VF at 5 seconds after shock). All published studies support the effectiveness (consistently in the range of 85%–98%)138of biphasic shocks using 200 J or less for the first shock.

Based on the above, this is the indication as to why the first dose of electricity is 200J.

In addition, another study referenced in the guidelines found that recurrence of VF “did not affect ultimate shock success, ROSC, or discharge survival.141

In summary, evidence shows that there is a high first success shock rate and recurrence of a shockable rhythm did not affect ultimate shock success. Our recommendation would be to shock at re-arrest patient at 200J.